Question

Currently I have the following code, working with Node.js, socket.io and Redis:

var io = require('socket.io'), redis = require("redis"), client = redis.createClient();
io.sockets.on('connection', function (socket) {
  var socket_id = socket.id;
  socket.on('chat', function(data) { 
      client.set('user:' + socket_id, data['colour']);         
      // The user left the page. Remove them from Redis.
      socket.on('disconnect', function () {
          client.del('user:' + socket_id);
          client.quit();
      });
  });
});

This works fine for normal socket connections and disconnections, but there seems to be a problem if Node goes down, or if I just restart Node as part of normal development.

The key is never deleted from Redis. So the number of entries stored in the Redis database gradually grows and grows. I’m also not sure whether the Redis client exists cleanly.

How can I clean up Redis entries and quit the Redis client when Node exits, as well as when the socket disconnects?

Answer 1

You could handle this when node exits, but e.g. in case the power goes down, there’s no way you can clean it up at shutdown time. I’d wipe old stuff from the DB at startup time instead.